render content and log the error when getting sibling urls

cms/djangoapps/contentstore/utils.py

@@ -550,7 +550,7 @@ def get_sibling_urls(subsection):
             # section.get_parent SHOULD return the course, but for some reason, it might not
             sections = section.get_parent().get_children()
         except AttributeError:
-            log.error(u"Error retrieving URLs in subsection {subsection} included in section {section}".format(
+            log.error(u"URL Retrieval Error # 1: subsection {subsection} included in section {section}".format(
                 section=section.location,
                 subsection=subsection.location
             ))
@@ -563,12 +563,19 @@ def get_sibling_urls(subsection):
             except IndexError:
                 pass
     if not next_loc:
-        sections = section.get_parent().get_children()
         try:
-            next_section = sections[sections.index(section) + 1]
-            next_loc = next_section.get_children()[0].get_children()[0].location
-        except IndexError:
-            pass
+            sections = section.get_parent().get_children()
+        except AttributeError:
+            log.error(u"URL Retrieval Error # 2: subsection {subsection} included in section {section}".format(
+                section=section.location,
+                subsection=subsection.location
+            ))
+        else:
+            try:
+                next_section = sections[sections.index(section) + 1]
+                next_loc = next_section.get_children()[0].get_children()[0].location
+            except IndexError:
+                pass
     if prev_loc:
         prev_url = reverse_usage_url('container_handler', prev_loc)
     if next_loc: